With the recent widespread development and application of personal computing, the industry has seen an increased interest and development of personal computers which are portable. Typically, these portable computers are not much larger than a small portable typewriter, but contain their own built-in CPU (Central Processing Unit), memory, disk drives, keyboard, carrying handle and display. The latter is typically a liquid crystal display contained on one side of a panel which folds down flat on the upper surface of the computer and serves as a cover to protect the keyboard and the display during storage and traveling.
For cosmetic as well as functional reasons, it is desirable that the display panel, including hinging hardward, fold to be flush with the upper surface of the computer, and this is typically accomplished by accommodating the panel within a stepped recess within the computer upper surface in which the keyboard is also located.
Ergonometrically, it is desirable for the keyboard to be slanted upwards slightly, relative to the horizontal plane so that the operator can manipulate the keys with facility. Similarly, it is desirable that the display fold open to a position somewhat greater than the vertical plane, i.e., to an angle of about 120-140 degrees, both to permit the operator seated before the machine to view the screen without crouching, and to position the screen properly for liquid crystal reflection of overhead light. Thus, it is desirable to have a flush hinge that is combined with a hold-open provision which premits the operator to rotate the screen from a fully-closed position to a first using position somewhere between about 90 degrees and 140 degrees and to retain the display in that position while the screen is viewed by the seated operator.
However, in some applications, and particularly with portable computers, it is desirable that the screen of the display be viewable by a standing operator. Thus, for example, the operator may wish to place the computer on a table or lab bench which is higher than the usual business desk and stand at that position while manipulating the computer's keyboard and viewing the dtata displayed. It is therefore also desirable for the display's hinging mechanism to permit the screen of the display to be rotated nearly all the way back, i.e., to a fully-opened angular position of nearly 180 degrees relative to the horizontal. Again, given the operator's position in front of the computer, as well as the need for properly reflecting overhead light from the liquid crystal display for adequate visibility of the characters, it is desirable that the screen be angled slightly from the horizontal, i.e., on the order of about 175 degreees for comfortable viewing by the operator.
Those skilled in the art will recognize that a simple hinge will permit a recessed display to be hinged to a position of somewhere between 0-180 degrees with little difficulty. However, in order to accomplish this, the centerline of the hinging mechanism must reside above the surface of the computer, and the advantages of having a flush surface are lost. If the hinging axis of the hinge is dropped below the surface of the computer, the display will be limited in its rotational travel by contact with upper edge of the recess at about 90 degrees maximum rotation, for a right-angle stepped recess. If the step into the recess is slanted from the vertical to permit further rotation of the display, a gap is created between the display and the computer which serves as a trap for dirt and debris and creates an unattractive appearance.
In an effort to overcome these disadvantages, some have incorporated a "double hinge" mechanism, i.e., one which hinges a pair of hinges to one another along one edge, the other edges of which are then hinged to the computer and display, respectively.
Hinges which combine a hold-open feature are known in the art. For example, U.S. Pat. No. 313,457 to Tuerk teaches a hinge for a door incorporating a convoluted spring and follower arm cooperating to hold the door in a fixed plurality of positions between a fully-opened and fully-closed position.
Thomas, in U.S. Pat. No. 2,388,021, discloses a leaf-spring in combination with a follower arm and rolling surface which serves to hold the door in an automobile in a fully opened position and, when sprung, to force the door toward the fully-closed position.
Similarly, U.S. Pat. No. 3,124,829 to DeVito teaches a hinge embodying a one-position hold-open feature.
U.S. Pat. No. 3,465,381 to Lawrie, et al., teaches a flush hinge for a cover plate on a sewing machine frame which incorporates a bifurcated spring which applies opening and closing force to the cover, depending whether the cover is in an opened or closed position.
Only two of these references teach a flush hinge; and none teaches a flush hinge combined with a hold-open provision permitting a selectable opened position between about 90 degrees and 180 degrees relative to the mounting surface. Further, none of these patents involve the unique relating to portable data-processors, as discussed above.